thanks for posting the issue / pictures regarding the piston-valve clearance. Years ago i had a set of high-lift cams made/welded, and ran into the same clearance issue on stock pistons... which inevitably lead to giving up on them. You may have just reinvigorated my desire to use them!

Blake

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"At first it's like a new pair of underware... Frustrating and constrictive. But then, it kind of grows on you..."

Not sure what your plan is to increase PV clearance but thought I would share how I did the work...

Fit cylinders to the crankcase (pistons without rings).Move piston to TDCInstall head gasket and cylinder head with valve (no valve springs)Measure valve movement with dial indicator; seat to top of pistonCompare with valve liftCalculate material depth to be removed from top of piston

Using an old cylinder head and an old valve I removed the required material from the top of pistonThe cylinder head was the guide for where to remove materialVelcro was used to stick abrasive material to the valveThe valve was spun using a cordless drill and an extension.I used varying grit size to complete cutting the piston to the required depth In my case it was 2mm or 0.080"

The top of piston needed to be finished using a die grinder, file and fine abrasive material (wet sanding)

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You do not need a therapist if you own a motorcycle, any kind of motorcycle! Dan Aykroyd

Not to derail the current line of interaction, but in regard to this changing of stroke entailing the diminishing of the journal size: the original journal/rod did seize, and now the journal is smaller, which means there is less surface area to support he increased load of the increased piston size. In this context, have you made any 'adjustments' to increase the oiling of these parts? Better oil? Higher volume oil pump? or?

The chase for more power exposes the weakest link(s) in the system, and we already know of the potential for the rod to tie up.

Also, how does the new motor feel when under power? When you are coming out of a turn on the gas? Is it buzzy or smooth?

One other thought on the oil pressure thing; there is a seal in the right hand case cover that is held in place with a circlip. This seal has to carry the oil pressure for the system or the pressure drops. The point is that this seal can easily be damaged upon assembly if you are not careful, and it is a critically important part if it fails to hold the pressure. Just another thing to check before reassembly. I think it was Tiger that suggested to replace that seal every time that case was removed, just to be safe.

The points you made regarding the crankshaft are valid and to add to them, the width of a Busa rod is significantly less than the stock rod. The lesser width is why the rod is piston guided.

Motorcycle 10W40 oil.

The motor felt great and when I get the jetting sorted I'm sure it will be that much better. I was at 145 main fuel and I am still lean. It's been a busy fall and cold came early to October so I have taken time to play lately.

It does have a small rpm range around 7,500 where vibration can be felt. I assume due to the elimination of the balance shaft. When in this range my left hand becomes anxious. So far so good though.

I recognized the seal on the end of the crankshaft is critical and a new one was installed when assembling.

Not sure what you meant regarding derailing the interaction...however just so others know...This engine build isn't proven and may be a huge waste of time and money...100 plus lb piece of scrap metal with the belly pan holding 2-1/2 litres of oil. Simply sharing for the sake of interest. My fun may end abruptly.

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You do not need a therapist if you own a motorcycle, any kind of motorcycle! Dan Aykroyd

Dean, the fact that something could go wrong is part of racing. The components are all stressed to their limits, and as long as they hold together the Fun happens. It is truly amazing how well things can go when everything is working, and also it can go from flash to trash in a couple seconds.

Hopefully you never find a small part on your work bench AFTER the engine has been closed up.

It would be very enlightening to find out why it is that the rear cyl. rod bearing is always the one to spin. It's almost like the oil passage in the crank doesn't deliver enough oil to the rear cyl. rod bearing, but if I remember right it is the closer bearing to the oil supply.

For stock piston replacement, I wonder if the pistons from the 4afe motor might be a good choice... same bore size, and wrist pin size but this engine is a very narrow valve angle 4 valve per cylinder motor unlike the very wide valve angle of the 4age.

Pretty sure the deck height is similar. Might be a very simple way to get new pistons and rings into a Vision.